1. Field of the Invention
Oil, gas, water and geothermal wells are typically drilled with a drill bit connected to a hollow drill string which is inserted into a well casing cemented in the well bore. A drilling head is attached to the well casing, wellhead or to an associated blowout preventer to seal the interior of the well bore from the surface. The drilling head also facilitates forced circulation of drilling fluid through the well while drilling or diverting drilling fluids away from the well. Drilling fluids include, but are not limited to, water, steam, drilling muds, air, and other gases.
Such drilling fluids should remain within the well. Spillage of the drilling fluids inconvenience workers and costs money and time. Furthermore, the stripper rubber connection should be made quickly and achieve a fluid tight seal.
However, casing typically includes various diameter sections. Thus, the rubber was sized to maintain sealing contact with the casing or the smallest diameter component which traveled through the well. The rubber must be rigid enough to withstand the pressures of the drilling fluid yet resilient enough to maintain a seal on the casing and other tools as the casing and other tools pass through the well.
Present day drilling operations are extremely expensive, and an effort to increase the overall efficiency of the drilling operation while minimizing expense requires the essentially continuous operation of the drilling rig. Thus, it is imperative that downtime be minimized.
In this regard, there is a need for improved sealing of the casing and allowing different sized casing and other tools through the casing stripper.
Pressure control is achieved by means of one or more stripper rubbers. Stripper rubbers typically taper downward and include rubber or other elastomeric substrate so that the downhole pressure pushes up on the rubber, pressing the rubber against the casing inserted into the stripper rubber to achieve a fluid-tight seal.
Casing stripper rubbers are connected or adapted to the drilling nipple at the nipple base to establish and maintain the pressure control seal around a down hole tubular (i.e. casing, etc.). The casing striper rubber replaces the bearing assembly when running casing and is especially useful in containing cement or drilling fluid returning to the surface. Casing stripper rubber sizes usually vary from 4½ inches to 13⅜ inches oversized.
Known casing stripper rubbers attach via a threaded connection to the drilling nipple. The threaded connection requires a specialized casing stripper rubber with internal threads. These specialized strippers can only be attached to threaded connections. Such threaded connections create difficulties when attaching and removing the casing stripper rubber. Dirt and other debris found on the drilling nipple increase the difficulty of attaching the casing stripper rubber to the drilling nipple. After use of the casing stripper rubber, users must remove the casing stripper rubber from the drilling nipple. The threaded connection of the casing stripper rubber increases the difficulty of removing the casing stripper rubber from the drilling nipple. In most instances, users cannot remove the casing stripper rubber from the drilling nipple. Users must either cut the casing stripper rubber from the drilling nipple or otherwise destroy the casing stripper rubber to remove the casing stripper rubber.
Cutting and otherwise destroying the casing stripper rubber requires additional time and effort for removing the casing stripper rubber. The casing stripper rubber attachment of the present invention improves the speed and efficiency of attaching and removing the casing stripper rubber. The improved efficiency of attaching and removing the casing stripper rubber decreases the drilling costs by reducing downtime of the operation. Furthermore, the present invention reduces the costs of manufacturing the casing stripper rubber. Furthermore, the casing stripper rubber of the present invention provides a greener solution than the known art. The casing stripper rubber of the present invention reduces the harmful environmental effects of removing the known casing stripper rubbers.
Therefore, a casing stripper rubber assembly that overcomes abovementioned and other known and yet to be discovered drawbacks associated with known casing stripper rubber assemblies individually and, optionally, would be advantageous, desirable and useful.
2. Description of the Known Art
Patents and patent applications disclosing relevant information are disclosed below. These patents and patent applications are hereby expressly incorporated by reference in their entirety.
U.S. Pat. No. 7,717,168 (“the '168 patent”) issued to Williams et al. on May 18, 2010 teaches a reinforced stripper rubber assembly with a stripper rubber body including a drillstring engaging portion having a drillstring bore extending axially therethrough. The drillstring engaging portion of the stripper rubber body taught by the '168 patent is made from an elastomeric material, has an inner surface that engages a drillstring when the drillstring is disposed therein and has a reinforcing insert receiving recess within an exterior surface thereof extending at least partially around the drillstring bore. The '168 patent teaches that a reinforcing insert is disposed within the reinforcing insert receiving recess. The reinforcing insert taught by the '168 patent includes an elastomeric material bonded to the stripper rubber body within the reinforcing insert receiving recess. A support structure taught by the '168 patent is disposed within a support structure engaging portion of the stripper rubber body. The support structure taught by the '168 patent includes a central opening generally aligned with the drillstring bore thereby allowing the drillstring to pass jointly through the central opening and the drillstring bore.
U.S. Pat. No. 7,717,170 (“the '170 patent”) issued to Williams on May 18, 2010 teaches an upper stripper rubber canister system comprising a canister body and a canister body lid. The canister body taught by the '170 patent includes an upper end portion, a lower end portion and a central passage extending therebetween. The central passage taught by the '170 patent is configured for having a stripper rubber assembly disposed therein. The upper end portion of the body includes a plurality of bayonet connector structures. The canister body lid taught by the '170 patent includes an exterior surface, an upper end portion, a lower end portion and a central passage extending between the end portions thereof. The '170 patent teaches that the exterior surface is configured for fitting within the central passage of the canister body. The canister body lid taught by the '170 patent includes a plurality of bayonet connector structures integral with its exterior surface. Each canister body lid bayonet connector structure taught by the '170 patent is configured for being engaged with one of the canister body bayonet connector structures for interlocking the canister body lid with the canister body.
U.S. Pat. No. 5,062,479 (“the '479 patent”) issued to Bailey, et al. on Nov. 5, 1991 teaches a stripper rubber for use in a drilling head to seal against a work string deployable through the drilling head. The stripper rubber taught by the '479 patent is longitudinally restrained to prevent extrusion of the stripper under pressure and to reduce the tensile and compressive stresses on the stripper rubber. The '479 patent teaches one embodiment of the stripper rubber that incorporates upper and lower metal rings which are maintained in spaced apart relation by vertical rods thereby allowing radial expansion as tool joints pass through the rubber but prevents inversion of the stripper rubber under pressure. The '479 patent teaches a second embodiment that bonds a stripper rubber into a cylinder which restrains the rubber in the vertical direction. Radial deflection is accommodated by allowing the rubber to flow vertically as a tool joint passes therethrough. Each of the stripper rubbers taught by the '479 patent incorporates an integrally formed drive bushing which facilitates mounting within the drilling head.
U.S. Pat. No. 5,213,158 (“the '158 patent”) issued to Bailey, et al. on May 25, 1993 teaches a drilling head with dual rotating stripper rubbers designed for high pressure drilling operations ensuring sealing under the extreme conditions of high flow or high pressure wells such as horizontal drilling. The dual stripper rubbers taught by the '158 patent seal on the same diameter yet are manufactured of different materials for different sealing functions. The lower stripper rubber is manufactured from a more rigid, abrasive resistant material to divert the flow from the well. The upper stripper rubber is manufactured of a softer sealing material that will closely conform to the outer diameter of the drill string thereby preventing the flow of fluids through the drilling head.
U.S. Pat. No. 5,647,444 issued to Williams on Jul. 15, 1997 (“the '444 patent”) discloses a rotating blowout preventor having at least two rotating stripper rubber seals which provide a continuous seal about a drilling string having drilling string components of varying diameter. A stationary bowl taught by the '444 patent is designed to support a blowout preventor bearing assembly and receives a swivel ball that cooperates with the bowl to self-align the blowout preventor bearing assembly and the swivel ball with respect to the fixed bowl. The '444 patent teaches that chilled water is circulated through the seal boxes of the blowout preventor bearing assembly and liquid such as water is pumped into the bearing assembly annulus between the stripper rubbers to offset well pressure on the stripper rubbers.